1. Field of the Invention
Molding compositions comprising acetal polymers having a high degree of crystallinity at room temperature have been in commercial use for many years. They have application in a wide variety of end uses, e.g., automobile applications such as bumper extensions and instrument panels, plumbing supplies such as valves, shower assemblies, flush tank components, faucets and pipe fittings, tool components such as screw driver adaptors, and household and personal products, such as quick boiling electric water kettles.
These crystalline acetal polymers have a highly favorable spectrum of physical properties which are responsible for their wide commercial acceptance. However, for certain applications, an improved capacity of the latter crystalline polymers for being blended into stable homogeneous molding compositions with other components such as certain stabilizers, would be highly desirable. Moreover, for some end uses, e.g., molded parts subjected to recurring mechanical stress, a higher degree of elasticity would be advantageous. Furthermore it may be beneficial when the crystalline acetal polymer is utilized in the fabrication of various articles, e.g., those involving a laminated structure or the use of reinforcing materials in the interior of a molded article, for there to be a greater degree of adhesiveness between the surface of the acetal polymer and another surface, e.g., of metal.
This invention relates to novel improved compositions comprising a moldable acetal polymer which contains a major proportion of oxymethylene units in the polymer chain and a high degree of crystallinity at room temperature. For example, the compositions are capable of forming mixtures with additives such as stabilizers which are fixed to a greater degree than previously. Moreover, the compositions have improved morphology over previously utilized compositions, which makes possible their being fabricated into articles having a higher degree of elasticity and adhesiveness.
2. Description of Related Art
The following prior art references are disclosed in accordance with the terms of 37 CFR 1.56, 1.97 and 1.98.
U.S. Pat. No. 3,639,192, issued Feb. 1, 1972 to Burg et al., discloses for use as adhesives copolymers of formaldehyde or trioxane with 1 to 60% by weight, preferably 1 to 30% by weight, of a cyclic ether, cyclic and/or linear acetal, e.g., 1,3-dioxolane, and/or an alkyl glycidyl formal, polyglycol diglycidyl ether or bis (alkane triol) triformal. Example 5 discloses a terpolymer of 97.95 wt. % of trioxane, 2 wt. % of ethylene oxide, and 0.05 wt. % of 1,4-butanediol diglycidyl ether.
U.S. Pat. No. 3,337,507, issued Aug. 22, 1967 to Gutweiler et al., teaches the formation of high molecular weight copolymers obtained by polymerizing a mixture of trioxane and any of certain polyformals. Example 4 of the patent shows the use of a polyformal which is a clear highly viscous oil at 70.degree. C. obtained by polymerizing a mixture of 1/3 mole of trioxane and 1 mole of dioxolane in the presence of p-nitrophenyl-diazonium fluoroborate as catalyst.
Japanese Kokai Sho 42-22065 of Yamaguchi et al., published Oct. 30, 1967, discloses copolymers of trioxane and an aperiodic ring compound, e.g., 1,3-dioxolane, prepared in liquid sulfur dioxide, and in Example 1 shows a copolymer of trioxane and 64 mol % of 1,3-dioxolane.
None of the foregoing references teaches any of the specific elastomeric, normally non-crystalline copolymers which are a component of the compositions of this invention, or the blending of any of such elastomeric copolymers with a normally crystalline acetal polymer.
Pending application Ser. No. 243,381, filed Sept. 12, 1988 by Collins et al., discloses and claims the elastomeric copolymers utilized in the compositions of this invention and states that they are useful as blending and adhesive agents for conventional crystalline acetal polymers. The entire disclosure of this application is incorporated by reference.
Pending application Ser. No. 255,569 filed October 11, 1988 by Collins et al., discloses and claims bonded articles, e.g., of conventional crystalline acetal polymers, wherein the bonding agents are the elastomeric, normally non-crystalline copolymers utilized in the compositions of this invention.